This invention relates to a method of giving a rust preventing wax treatment to an article, such as an automobile body for example.
A rust preventing wax treatment is given to many kinds of industrially produced articles.
In the automobile industry it is usual to make a rust preventing wax treatment of automobile bodies which are already provided with a finish coat. In this treatment a wax is applied to selected parts of the car body such as side members, inner surfaces of the engine room hood and the trunk lid and inboard surfaces of doors. It is desired to form a wax coating film of a predetermined thickness on every area of the surfaces subjected to treatment, and the wax must penetrate into narrow spaces that exist, for example, in joint regions and panel turnup regions of each car body. The penetration of the wax into narrow spaces is facilitated if the wax exhibits a very low viscosity. However, when such a low viscosity wax is used it is difficult to form a wax coating film of a desired thickness on every area, and the wax applied to upright or steeply slant surfaces continues to drip down even after completion of the wax treatment operation. Such dripping of the wax often causes soiling of the treated automobile bodies or the subsequent station of the production line. If it is intended to obviate such disadvantages by using a wax having a sufficiently high viscosity, the wax fails to penetrate into narrow spaces so that the rust preventing treatment remains incomplete.
With a view to realizing good penetration of a wax into narrow spaces in the object of wax treatment without suffering from dripping of the applied wax, it is known to utilize a thixotropic property which some kinds of waxes possess. When a wax possesses a thixotropic property, the viscosity of the wax becomes relatively low while the wax is in motion by the effect of an externally supplied mechanical energy and reverts to a relatively high level as the wax resumes static state. However, the waxes used in conventional rust preventing treatments are not sufficiently high in the degree of thixotropy. Therefore, it is usual to use a wax composition of either a solvent-thinned type or an aqueous dispersion type in which the content of the organic solvent or water is relatively large. By using such a liquid wax composition which is sufficiently low in viscosity good penetration of the wax into narrow spaces is achieved. However, solidification of the applied wax by evaporation of the solvent takes a considerable time, so that the wax applied to upright or steeply slant surfaces often drips down before sufficiently increasing viscosity. That is, difficulties in forming a wax coating film of a desired thickness and the likelihood of soiling of the treated automobile bodies or the subsequent operation station are still remaining as unsolved problems.